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Wez Furlong 33f25e9ce6
reduce latency when heavily using foreground process info
The tcgetpgrp call appears to have high variance in latency, ranging
from 200-700us on my system.

If you have 10 tabs and mouse over the tab bar, that's around 7ms
spent per frame just figuring out the foreground process; that doesn't
include actually extracting the process executable or current working
directory paths.

This was exacerbated by the mouse move events triggering a tab bar
recompute on every pixel of mouse movement.

This commit takes the following steps to resolve this:

* We now only re-compute the tab bar when the UI item is changed by
  a mouse movement
* A simple single-item cache is now used on unix that allows the caller
  to proceed quickly with stale-but-probably-still-mostly-accurate data
  while queuing up an update to a background thread which can absorb
  the latency.

The result of this is that hovering over several tabs in quick
succession no longer takes a noticeable length of time to render the
hover, but the consequence is that the contents of a given tab may be
stale by 300-400ms.

I think that trade-off is worth while.

We already have a similar trade-off on Windows, although we don't
yet do the updates in a different thread on Windows. Perhaps in
a follow up commit?

refs: https://github.com/wez/wezterm/issues/2991
2023-01-21 15:25:57 -07:00
..
examples fixup build for pty api change 2022-08-12 08:45:02 -07:00
src reduce latency when heavily using foreground process info 2023-01-21 15:25:57 -07:00
tests deps: remove pretty_env_loggger 2022-04-07 08:24:07 -07:00
Cargo.toml update base64, work around another batch of breaking API changes 2023-01-08 18:49:45 -07:00
LICENSE.md Add missing license files 2022-08-17 07:19:12 -07:00